Extraction of coffee



Patented Feb. 1, 1944 EXTRACTION F COFFEE William Kappenberg, QueensVillage, and Frank J. Bameh, New York, N. Y., assignors to OofleeProducts Corporation, New York, N.-Y., a corporation of New York NoDrawing. mums May 22, 1942.

Serial No. 444,044

- 9 Claims. (01. 99-41) This invention relates-to improvements in theproduction of concentrated coflee extracts or coffee concentrates.

This application is a continuation-in-part of my prior applicationSerial No. 280,059, filed June 20,1939.

It has-previously been proposed to produce liquid or dry extracts ofcoffee by various processes, including extraction with hot waterfollowed by concentration, for example, under a vacuum; extraction withhot or cold water countercurrently, bringing the water into contact withsufilcient masses of cofiee so that the final product is concentratedand does not require concentration; soaking coffee in water andsubsequently expressing under high pressures, etc. However, none ofthese previously proposed processes has yielded a commercially feasibleproduct, either because of the fact that the products produced, whendiluted with hot or boiling water, do not give beverages approximatingfreshly brewed coffee, or because of low yield, or prohibitiveproduction cost, or lack of control of the quality of the product.

The present invention provides processes by which concentrated cofieeextracts, which when diluted with hot or boiling water give brewscomparable with freshly brewed coffee from the same type of bean, may beproduced by subjecting ground roasted coffee to what may be termedcountercurrent extraction with cool or coldwater, that is, water at atemperature of about 100 F., or lower, advantageously below 85 F. underoperating conditions such that substantially all of the desirableextractible matter is extracted from the coffee while the throughput ismaintained suillciently high so that the operating cost is low and thetime of contact of the water with the cofiee is not so great as to causeobjectionable changes in flavor and aroma. The process is carried out bypassing water through a mass or a series of masses of cofiee, usingsulficient initial pressure on the water to insure proper flow throughthe coflee. tion of the coffee through which the fresh water passesnaturally becomes exhausted first, while the successive portions ormasses are extracted to successively lesser degrees because of thincrease in concentration of extractibles in the treating water.Accordingly, when the intial portion of the coffee or first mass in theseries is sufficiently leached, it is removed from the system and acorresponding fresh mass or quantity 1 introduced at the other end ofthe extraction system,

The initial porwater comes into contact has previously been subjected tosuccessive extractions with coflfee extracts of decreasingconcentration, while the final concentrate is that which passes throughthe fresh coffee.

In carrying out this process, it was found that irregularity inoperation, for example, with respect to the rate at which the water,under any given pressure, would flow through the coffee, the proportionof water soluble material extracted, etc., varied widely, and that theextraction could I not be carried out with any reasonable assurance ofproper operation or sufliciently complete extraction to make the processcommercially feasible.

The present invention includes improvements in this type of processwhich permit high yield,

i. e., substantially complete extraction of the extractible constituentsof the coffee; continuous operation without channelling, clogging,building up of high back-pressures and the like: high throughput oroutput from given apparatus at low cost; and the production of a productof con sistently high concentration and quality.

In accordance with the present invention, the fresh masses of coffee arewetted or dampened with water, or aqueous liquids including skimmedmink, aqueous alcohol, aqueous glycerol, sugar solutions and/or thelike, befor passing through them the extract from the preceding massesof coffee.

Th amount of water used to wet the roasted ground coffee before passingthe extracting liquid through it may be varied, but the amount usedshould be sufflcient to cause rather complete expansion of the coffeewhile not so great as to form a mud or slurry, or to dilute the finalcoffee concentrate too much.

Advantageously from about eight to about sixteen ounces, preferablyabout twelve ounces of water per pound of solids, usually only cofiee,is used. Dissolved or suspended matter in the Drewetting liquid is to bconsidered as solids. The prewetting liquid should be uniformlydistributed throughout the mass of coffee, as by spraying it withagitation of the coffee, etc. Eighteen to so that the portion of coffeewith which fresh above may be used for any grind which is feasibly orten ounces per pound of coffee.

extracted. The concentration of the extract obtained will depend to someextent on the amount of liquid used for prewetting. To obtain highlyconcentrated extracts, relatively small amounts of liquid should be usedfor prewetting, e. g., eight If less concentrated extracts areunobjectionable, larger quantities of water, e. g., fourteen to sixteenounces per pound, may be used with advantage. However, for generaloperation, the prewetting with three-quarter pounds of water to onepound of solids gives optimum results.

The wetted cofiee after expansion is transpacked either by hand ormechanically toa density that must be within certain rather narrowlimits to permit proper operability. It has been found that the densitymust be within the range of thirty-four to forty-five pounds of wettedcofi'ee per cubic foot and for most efficient results advantageouslyshould be forty and forty-two pounds per cubic foot. 11' these limitsare not met very great operational dimculties are encountered and morespecifically the extraction chambers such as pipes, tubes, columns,towers orconveyors will jam and so preventpassage of extraction liquids.In other cases, channeling or by-passing with resultant low extractionyields, and concentrates of low and uneconomical gravity are obtained.Finally it is not feasible to dampen or pre-wet the fresh coffee in theextraction chamber because it cannot be evenly wetted and, more serious,it expands when wetted within the restricted space thus causing theformation of dense masses and consequent jamming. By such prewetting andcontrolled packing of the coffee, more consistent results are obtained,more finely ground coffee can be used, the throughput can be greatlyincreased, that is, the time required to extract a given quantity ofcofi'ee in a given apparatus may be greatly decreased, and theproportion of extractible material extracted may be radically increased.Perhaps the most important advantage is the fact that with suchprewetting of the coffee, a high proportion of the desirable extractiblema! terial is consistently extracted and carried into the concentrate.The greatest expense in the production of coffee extracts is in the costof the roasted coffee required, and a more thorough extraction naturallyreflects a greater yield of concentrate of given flavoring value from agiven quantity of cofi'ee.

An advantageous method of. extracting the coffee in accordance with theinvention is with the use of a series of vertical tubes, withconnections from the top of one tube to the bottom of the next. 'Withsuch apparatus, fresh water may enter at the bottomof the first tube,flow upwardly through the coffee in the tube, and from. the top of thistube pass to the bottom of the second tube and progress in this mannerthrough each of the tubes until the desired concentrate is dischargedfrom the top ofthe last tube. When the coffee in the first tube issufiiciently extracted, it is removed from the apparatus and a tubecontaining fresh coffee is attached at the opposite end of the series.The

fresh coffee, before introduction into thistube. and before the extractfrom the previous tubes is caused to flow through it, iswet or dampened,as described hereinbefore, with an appropriate quantity of water andpacked to the proper density to insure regularity of flow and properextractions.

It is important to provide at the outlet of each tube a bed of rathercoarse filtering material. inert with respect to the coffee extract, e.g., 20 to 30 mesh granules, coarse fibrous material or the like, such assand, metal shavings or other suitable material. The bed need not bevery deep, 1. e., one to two inches is generally sufiicient, but itsprovision is important, because without it, the screen or cloth used tohold the coffee in the tube becomes clogged, with the result that theextracting liquid passes through the screen or cloth with difilculty,and in a short time may cease to flow.

Other types of apparatus than that referred to may, of course, be usedin carrying out the process. For example, instead of providing a seriesof vertical tubes in series, a single vertical tube may be provided, andthe process may be carried out by introducing water at the bottom andtaking coffee extract from the top, with removal, at intervalsdetermined by the extent of extraction, of portions of the'extractedcofiee from the bottom and introduction of fresh, dampened or prewettedcoffee at the top, a suitable filtering layer being provided at the topof each successively introduced mass of-cofiee.

The invention will'be further illustrated by the following specificdescription, but it is not limited thereto.

Roasted bean cofiee, Santos #3, rather finely ground, having a screenanalysis of 27.1% retained on a 20 mesh screen, 54.7% retained on a 40mesh screen and 28.2% passing a 40 mesh screen is thoroughly mixed withtwelve ounces of water per pound of coffee and introduced into threevertical tubes each six feet long and four inches in inner diameter. Thecoffee is introduced in successive portions with intermediate tamping toa density of about forty-two pounds per cubic foot. A layer of sand twoinches thick is placed on top of the tamped coffee in each tube. Screensare provided at the top and bottom of each tube to retain the sand layerand coffee in place. The top of the first tube is connected to thebottom of the second, and the top of the second to the bottom of thethird. Water at a temperature of about 70 to F. is introduced at thebottom of the first tube under an initial pressure of about twenty-fivepounds; the cofiee extract flowing from-the top of the third tube. Afterabout 0.82 gallons of extract is obtained,

the flrst tube is removed, the water inlet concoffee, the process beingcontinued in this fash ion with successive replacements of thecompletely extracted coffee with fresh coffee, one tube being replacedfor each 0.82 gallons of extract produced. After at least three tubeshave been replaced and removed in this fashion, the process isconsidered to be a countercurrent process, and the extract thus obtainedcontains around 27% solids, which is almost all of the material whichcan be extracted from the coffee. 'In the course of the operation, theinitial pressure is maintained uniformly between twenty-five and ninetypounds per square inch gage, preferably about 40 p. s. i., pressures ofthis order giving substantially. constant results. Five cc. of theextract, when diluted with hot or boiling water, gives a cup of brewfully comparable to freshly prepared coffee brew made from the same typeof bean by conventional means. The coffee concentrate so obtainedrequires no further concentration before being taken to dryne s with orwithout additional agents such as sugars and the like.

In the operation described, three tubes, six feet long and four inchesin diameter, are used. so that the extracting liquid is passed through acolumn of ground coffee about eighteen feet long. Almost the sameresults may be obtained with the use of two such tubes, or five or sixsuch tubes; although asthe number of tubes is varied, it may benecessary to adjust somewhat the rate of flow of the extracting liquid,for example, by adjusting the pressure at which the water is supplied.As the length of the column of coffee is increased, as by the use ofmore tubes, the pressure at which the water is supplied must beincreased to maintain the throughput.

Although the above example describes the use of four-inch tubes, it hasbeen found in commercial'operation that tubes twelve inches in diameter,are equally satisfactory and more desirable from an output standpoint.The length of the column of coffee, the number of tubes used, the dameter of the tubes and the number thereof may be varied with goodresults. providing there is a sufliciently long column of coffee topermit adequate extraction and providing the initial pressure issuflicient, taken together with the prewetting, tamping and provision ofsuitable filtering beds, to provide the desired throughout.

In general. the amount of extracting liquid passed through the coffeegoverns the concentration of the soluble coffee in the final liquidcoffee concentrate. The rate of flow of the extracting liquid should besuch that a volum of water equal to the volume of coffee held in theapparatus will flow through the coffee in from one to four hours,preferably in about one and a half hours. Higher rates tend to build uphigh back-pressures and lower rates are uneconomical. An advantageous rae of flow yields 0.082 gallons of concentrated liquid coffee extract perpound of roasted coffee. This same liquid coffee concentrate contains2.6 pounds soluble coffee per gallon of concentrate.

The coffee concentrate obtained by the process of this invention is inastate of high concentration, hence great thermal economies are obtainedwhen taking the concentrated liquid coffee extract to dryness because nopreconcentration is required in most cases. Furthermore, the flavor andaroma characteristics of the finished dry product are improved becauseof the very greatly lowered time required to remove water in the dryingoperation proper.

The initial water pressure used may be varied over a wide range,depending mainly upon the rate of flow desired, the length of the columnof cofiee, and the fineness of the grind. Pressures in excess of fifteenpounds, e. g., up to 300 pounds or even more, are usually required forany reasonably economic rate of flow. Pressures of from twenty-five toone hundred fifty pounds are advantageously used.

The rate of flow, the effectiveness of extraction per unit volume ofaqueous solvent and hence the economic value of the process of thisinvention, will also depend upon the grind of the coffee. With finelyground cofiee'the rate of flow at any given pressure will generally besmaller than with more coarsely ground coffee; on the other hand, theextraction is more complete and uniform with the more finely groundcoffee. Ground coffee having a screen analysis of about 26% retained ona 20 mesh screen and 45% retained on a 40 mesh screen, with theremainder passing a 40 mesh screen, gives excellent results. More finelyground coffee may be used, but tends to cut down the rate of flow. Morecoarsely ground coffee, for example, coffee with a. semen analysis ofabout retained on a 20 mesh screen and 25% on a 40 mesh screen with theremainder passing a 40 mesh screen, also gives excellent results. Coffeewith a screen analysis of about 2% retained on a 12 mesh screen, abouton a 20 mesh screen and about 15% on a. 40 mesh screen, with theremainder through a 40 mesh screen, is about as coarse as can be usedwith consistently high extraction, although again if the length of thecolumn of coffee is increased,

good results may be obtained with even coarser grinds.

- One of the important advantages of the process is that the timerequired for the extraction of any given amount of coffee is short, sothat the development of off-flavors, rancidity, or change by bacterialattack, molds, yeast or the like is avoided.

Instead of using water for the extraction of the roasted coffee, otheraqueous liquids, for ex-- ample, skimmed milk, sugar solutions, aqueouscoffee extracts, preferably concentrated, e. g., specific gravity ofabout 1.05 at F., or extracts of various materials, such as chicory, maybe used, with production of modified concentrates. The extract obtainedfrom the process varies slightly during the extraction depending on theprcwetting liquid and the degree and rate of extraction. The specificgravity is preferably between 1.1 to 1.2 at 110 F. Low concentration, e.g., specific gravity of 1.02 upto 1.07 at 110 F., are used as prewetliquids.

The extracting liquid may advantageously contain a small proportion of asuitable non-toxic,

unobjectionably flavored wetting or emulsifying agent, which seems topromote the extraction; and a small amourit of a non-toxic,unobjectionably flavored anti-oxidant, a number of which are available,may advantageously be incorporated in the concentrate, either byaddition to the concentrate or to the extracting liquid, to inhibit thedevelopment of objectionable flavors due to oxidation or change onstorage. Although coffee has been described hereinbefore as the materialto be extracted, it is possible to treat similarly other waterextractible granular food substances which form potable decoctions, suchas ground roasted barley, wheat and the like.

The product directly produced by the process of this invention is aliquid coffee concentrate. When diluted with hot or boiling water, ityields a beverage comparable to conventionally, freshly brewed coffee.The liquid product can, by a suitable spray drying process, as byspraying into a stream of hot air or other gas, e. g., concurrently orcountercurrently, be converted to a dry product which is soluble inwater, and retains substantially all of the desirable properties of theliquid concentrate, and hence, when dissolved in hot or boiling water,yields a beverage fully equivalent to freshly brewed coffee. Or theliquid can be converted to an excellent dry product by vacuum dryingprocesses, e. g., vacuum drum drying.

As many widely varying embodiments of the present invention may be madewithout departing from the spirit and scope thereof; it is to be un- Itially extracted ground roasted coifee.

2. The process of producing a. concentrated coffee extract whichcomprises producing a substan-' tially uniformly prewetted groundroasted cofl'ee by treating with water in an amount ranging from about 8to 16 ounces of water per pound of coffee, introducing said wettedcoffee into an extraction zone, tamping it to a substantially uniformdensity of about 34 to 45 pounds per cubic foot, and passing an aqueousliquid through said cofiee to obtain a coifee extract.

3. A countercurrent process of producing a concentrated coflee extractwhich comprises treating ground roasted coffee with an aqueous liquid inan amount varying from one-half to one pound of water per pound ofsolids, introducing said wetted coifee into an elongated extraction zoneat a substantially uniform density of about of inert filtering materialat the discharge from the extraction zone, passing through saidprewetted coflee in the extraction zone an aqueous extract of a groundroasted coflee. which cofieehas been previously partially extracted inthe previous cycle, to obtain a concentrated aqueous coflee extract,after a substantial extraction period similarly adding anotherextraction zone of fresh prewetted, tamped coffee to the extractionsystem, and removing a corresponding exhausted I '34 to 45 pounds percubic foot, providing a layer density between 34 and 45 coffee to obtaina coffee extract.

6. The process of producing a concentrated coffee extract whichcomprises producing a substantially uniformly prewetted ground roastedcoifee by treating with water in an amount ranging from about 8 to 16ounces of water per pound of coffee, introducing said wetted cofl'eeinto an extraction zone, tamping it to av substantially uniform densityof about 40 to 42 pounds per cubic foot, and passing an aqueous liquidthrough said coffee to obtain a coffee extract.-

7. The process of producing a concentrated coffee extract whichcomprises producing a bstantially uniformly prewetted ground roas dcoffee by treating with water in an amount of about 12 ounces of waterper pound of coffee, introducing said wetted cofl'ee into an extractionzone, tamping it to a substantially uniform density of about 40 to 42pounds per cubic foot, and passing an aqueous liquid through said coffeeto obtain a coffee extract.

8. The process of preparing a concentrated coffee extractwhich'comprises treating ground roasted coffee with a concentratedaqueous coffee extract in an amount varying from one-half to one poundof water to a pound of solids, providing an extraction bed of saidwetted coffee at a pounds per cubic foot,

and extracting it with an aqueous liquid.

9. The process of preparing a concentrated coffee extract whichcomprises prewetting ground roasted coffee with an aqueous liquid,forming a bed of said prewetted coilfee and compacting it to asubstantially uniform extent so that its density is above 34 pounds percubic foot but less than that value at which the coffee bed remainssubstantially impervious to an extracting liquid, and passing an aqueousliquid through the coffee bed to remove the cofiee extracts.

WILLIAM KAPPENBERG. FRANK J. RAMEH.

